The present invention relates to clothes pressing appliances, such as pressing irons or steam generators, having a reservoir for water that is subsequently converted into steam to assist a clothes-pressing operation.
Numerous techniques for fabricating such a reservoir are already known in the art. For example, the technique of blow molding is known, but is little used because it does not permit achievement of the precise dimensions necessary for mass production, given that the reservoirs are normally made in two parts that must be assembled together. Water tightness must then be achieved by providing a flexible seal that is compressed between the two parts, as described in German patent document DE 2 821 134, which requires a considerable amount of work for installing the seal. The two parts can also be joined by cementing or welding them together, as described in French patent document FR 2 322 233 or Japanese document JP60-183000, on assembly lines when they are made of plastic material, or by rolling and crimping of the edges when at least one part is of metal.
Thus, French patent No. FR 2318970 describes a water reservoir for a clothes pressing iron, the reservoir being made of two parts, one of which is transparent and the other of which is preferably of metal. The two parts are assembled together with a joint that is preferably of silicone and is elastic, the joint being interposed between the base and the cover of the reservoir.
In all of these techniques in which the reservoir is made of two parts that are assembled together, a substantial amount of time and materials are used on pressing iron assembly lines, whether this be for placing the joint, cementing, welding, or crimping, and it is necessary to have on hand a substantial number of parts that are awaiting assembly or are being operated on. This creates the risk of a delayed detection of defects in a lot of parts, and the difficulties of managing the two parts of each reservoir.
The patents JP 59-165632 or EP 683031 describe processes in which two parts are molded in a mold and then assembled together with a joint molded onto the two parts in the same mold. For this purpose, the mold is made of three parts including a central part which is movable or displaceable so that the other two mold parts containing the parts that have been molded in a first phase can be brought together and a joint can then be molded in a second phase on the perimeter of the other two parts that have been molded.
The patents JP 62-087315 and JP 61-193815 both describe processes having the same characteristics for producing a hollow body in the same mold in two successive cycles. The mold has two parts, one of which slides after a first phase of molding the two parts. In the second phase, the edges of the two parts are brought together and a joint is molded.
However, if appropriate precautions are not taken, a reservoir produced according to one of the prior art techniques and subjected to repeated temperature fluctuations, as inevitably occurs in clothes pressing irons, will with time experience leaks due to failure of the joint. Thus, these reservoirs are not highly durable.
A basic object of the invention is to overcome these drawbacks and difficulties.
Basically, the invention provides a method for the fabrication of clothes pressing iron water reservoirs made of two parts, in such a manner as to eliminate the need for storing parts upstream of the assembly stations for the reservoirs and eliminating specific means for sealing the reservoirs on the pressing iron production lines.
The invention also provides a reservoir made of two parts of injection molded plastic material, the reservoir having a sealing joint that is injection molded and intimately linked while hot to the two parts, constituting this reservoir, according to the method of the invention.
The method according to the invention achieves a high level of productivity, adapted to large-scale mass production.
More specifically, the invention provides a method for fabricating water reservoirs for clothes pressing irons, each reservoir being composed of two plastic parts, the method comprising: simultaneously molding the two parts of one reservoir in a first injection molding step in two impressions of the same mold; and assembling the two parts together while, in a second injection molding step, injection molding a joint of plastic material between the two parts to connect the two parts together in a fluid-tight manner, wherein the two parts are assembled together and the second injection molding step is performed before complete crystallization of the two parts.
Thus, the two parts that are molded in an injection molding cycle are immediately used and assembled in the following cycle without any intermediate storage. The molding machine delivers finished reservoirs ready to be installed in pressing irons. The molded parts are assembled before their complete crystallization and therefore while still soft so that they can easily conform to one another. In addition this allows the two parts and the sealing joint to easily conform to one another. During injection molding of the joint, the joint material, being in a softened or liquid state, supplies heat and softens or remelts the surface of each part of the reservoir. This is facilitated by the fact that the crystallization of these parts, or at least the portions in contact with the joint, has not yet been completed and thus local remelting of material of the parts in contact with the joint requires less energy.
Preferably, on the one hand the material of the joint, and on the other hand the material of each of the reservoir parts, are selected to be of identical composition or of compatible compositions in order to form alloys or in order to adhere well to one another. There is then locally produced a diffusion, a mixing, or an alloying between the materials of the joint and of each part. The crystallization of the constituent parts of the reservoir not having been completed at the moment of injection of the joint material, the crystals of the joint and of each part can be organized and bond together more easily at the junction, or interface, surfaces, which causes the bonding of the joint with each of the parts to be very solid.
According to a preferred version of the method of the invention, the two constituent parts of the reservoir are molded in two impressions of the mold, ejected before complete crystallization, and picked up and assembled in another impression of the same mold specifically provided for injection of the joint and assembly of the reservoir. A first reservoir that has just been assembled is ejected from its assembly impression and simultaneously the reservoir parts for the following reservoir, that were molded during assembly of the first reservoir are ejected and picked up for example by a robot arm which puts them in place in the assembly impression that is then empty. Thus, there is no intermediate storage of pair of reservoir parts.
According to another version of the method of he invention, the mold is composed of three parts, a first part having an impression of one of the parts of the reservoir, a second part of the mold having an impression of the other part of the reservoir and, between the first two parts of the mold, a central part having impressions, or recessed portions, that are complementary to the impressions of the first and second mold parts. The machine is constructed to provide two mold closing positions. When the three parts of the mold are closed against one another, the two parts of a reservoir are injection molded. Then the mold is opened without ejecting the reservoir parts from their impressions, after which the central part of the mold is withdrawn. The mold then having only its first two parts is closed again, placing the two corresponding reservoir parts in contact with one another. The joint is then injection molded into a space that has been left free between the reservoir parts and previously occupied by the central part of the mold. The mold is again opened and the finished reservoir is ejected without any handling of the reservoir parts having taken place. With respect to this version of the invention, the necessary operating cycle is doubled but the absence of manipulations can be a significant advantage.
The invention also provides a water reservoir for a clothes pressing iron, the reservoir comprising two plastic parts and a sealing joint joining the two parts together while forming a fluid-tight seal between the two parts, wherein the two plastic parts and the joint are injection molded, each of the plastic parts has an edge having a bearing and positioning face via which the plastic parts contact one another, the joint is a body that is injected molded to the edges to join the two parts together, and the parts and the joint are made of the same material or materials that are compatible with one another to form alloys or to adhere to one another.
Preferably, the two parts of the reservoir are formed to have, along their facing edges, faces for supporting on another. This permits a very precise assembly, the precision of which does not depend on the joint. In addition, the mutual supporting of the reservoir parts creates a tight seal opposing a flow of the injection molded joint, at least toward the interior of the reservoir.
Preferably, the supporting faces provided by the two parts of the reservoir are also centering faces. Thus, two reservoir parts, even though incompletely crystallized, can be assembled more easily.
In a preferred form of construction of the reservoir, the faces of the two reservoir parts that bear against one another include on a first part a groove that is of substantially trapezoidal cross-section along the edge of the first part, and on the second part a tapered edge of substantially trapezoidal cross-section, the edges of which are adjusted to the groove in the first part. The base of the groove of the first part and the peak of the edge of the second part are spaced apart and the joint is injected into that space. This arrangement permits centering of the parts with respect to one another and assures a tight seal during injection of the joint, so that the joint is not noticeable on the reservoir. In addition, since no surface of the joint is in contact with the mold, losses of heat are less rapid toward the mold and more of the heat is available to modify the surfaces of the edges of the reservoir parts.
Preferably at least one of the reservoir parts has, along the edge in contact with the joint, a raised portion of small cross-section with respect to the cross-section of the joint and in the form of a blade that penetrates into the joint. This thin raised portion is easily softened or remelted upon injection of the joint material, offering a high degree of certainty that at least in the zone where the raised portion is attached to its associated part, the bond between that part and the joint will be of high quality, thereby causing the result of the process to be more reliable.